---
title: "Systems Programming and Advanced Topics"
description: "Learn about Rust's systems programming features, including unsafe code, the macro system, performance optimization, and low-level programming."
---

# Systems Programming and Advanced Topics

## 📖 Learning Objectives

Understand Rust's systems-level programming features, learn to use unsafe code, the macro system, performance optimization techniques, and grasp low-level programming concepts.

---

## 🎯 Systems-Level Programming Comparison

### JavaScript's High-Level Abstraction

JavaScript runs in a virtual machine, providing high-level abstractions:

<UniversalEditor title="JavaScript High-Level Abstraction" compare={true}>
```javascript !! js
// Example of JavaScript's high-level abstraction
class MemoryManager {
    constructor() {
        this.memory = new Map();
        this.gcStats = {
            collections: 0,
            freedMemory: 0
        };
    }
    
    // Allocate memory (managed automatically by JavaScript)
    allocate(key, data) {
        this.memory.set(key, data);
        console.log(`Allocating memory for: ${key}`);
    }
    
    // Deallocate memory (handled by automatic garbage collection)
    deallocate(key) {
        this.memory.delete(key);
        console.log(`Deallocating memory for: ${key}`);
    }
    
    // Manually trigger garbage collection (only available in some environments)
    forceGarbageCollection() {
        if (global.gc) {
            global.gc();
            this.gcStats.collections++;
            console.log('Forcing garbage collection');
        }
    }
    
    // Memory usage statistics
    getMemoryUsage() {
        if (process.memoryUsage) {
            const usage = process.memoryUsage();
            return {
                rss: usage.rss,
                heapUsed: usage.heapUsed,
                heapTotal: usage.heapTotal,
                external: usage.external
            };
        }
        return null;
    }
}

// Usage example
const memoryManager = new MemoryManager();

// Allocate a large amount of data
for (let i = 0; i < 1000; i++) {
    memoryManager.allocate(`key${i}`, {
        id: i,
        data: 'x'.repeat(1000), // 1KB of data
        timestamp: Date.now()
    });
}

console.log('Memory usage:', memoryManager.getMemoryUsage());

// Deallocate some data
for (let i = 0; i < 500; i++) {
    memoryManager.deallocate(`key${i}`);
}

// Force garbage collection
memoryManager.forceGarbageCollection();

console.log('Memory usage after GC:', memoryManager.getMemoryUsage());

// Simulating low-level operations (limited in JavaScript)
class LowLevelOperations {
    // Simulate pointer operations (no real pointers in JavaScript)
    createPointer() {
        return {
            address: Math.random().toString(16),
            value: null,
            dereference() {
                return this.value;
            },
            assign(value) {
                this.value = value;
            }
        };
    }
    
    // Simulate memory layout
    createMemoryLayout() {
        return {
            stack: [],
            heap: new Map(),
            allocateOnStack(value) {
                this.stack.push(value);
                return this.stack.length - 1;
            },
            allocateOnHeap(key, value) {
                this.heap.set(key, value);
                return key;
            }
        };
    }
    
    // Simulate system calls
    systemCall(operation, data) {
        console.log(`System call: ${operation}`, data);
        // In a real environment, these operations are handled by the JS engine
        return {
            success: true,
            result: `Simulated result of ${operation}`,
            timestamp: Date.now()
        };
    }
}

// Using low-level operations
const lowLevel = new LowLevelOperations();

const pointer = lowLevel.createPointer();
pointer.assign("Hello, World!");
console.log("Pointer value:", pointer.dereference());

const memory = lowLevel.createMemoryLayout();
const stackAddr = memory.allocateOnStack(42);
const heapAddr = memory.allocateOnHeap("dynamic", "data");

console.log("Stack address:", stackAddr, "Value:", memory.stack[stackAddr]);
console.log("Heap address:", heapAddr, "Value:", memory.heap.get(heapAddr));

// Simulate a system call
const syscall = lowLevel.systemCall("read", { file: "test.txt", size: 1024 });
console.log("System call result:", syscall);
```
</UniversalEditor>

### Rust's Systems-Level Programming

Rust provides direct memory control and system-level access:

<UniversalEditor title="Rust Systems-Level Programming" compare={true}>
```rust !! rs
use std::alloc::{alloc, dealloc, Layout};
use std::collections::HashMap;
use std::ptr;
use std::mem;

// Custom memory manager
struct MemoryManager {
    allocations: HashMap<usize, Layout>,
    total_allocated: usize,
}

impl MemoryManager {
    fn new() -> Self {
        Self {
            allocations: HashMap::new(),
            total_allocated: 0,
        }
    }
    
    // Manually allocate memory
    unsafe fn allocate(&mut self, size: usize, align: usize) -> *mut u8 {
        let layout = Layout::from_size_align(size, align).unwrap();
        let ptr = alloc(layout);
        
        if !ptr.is_null() {
            self.allocations.insert(ptr as usize, layout);
            self.total_allocated += size;
            println!("Allocated {} bytes at {:p}", size, ptr);
        }
        
        ptr
    }
    
    // Manually deallocate memory
    unsafe fn deallocate(&mut self, ptr: *mut u8) {
        if let Some(layout) = self.allocations.remove(&(ptr as usize)) {
            dealloc(ptr, layout);
            self.total_allocated -= layout.size();
            println!("Deallocated {} bytes from {:p}", layout.size(), ptr);
        }
    }
    
    // Get memory usage statistics
    fn get_stats(&self) -> (usize, usize) {
        (self.total_allocated, self.allocations.len())
    }
}

// Smart pointer implementation
struct SmartPtr<T> {
    ptr: *mut T,
    manager: *mut MemoryManager,
}

impl<T> SmartPtr<T> {
    unsafe fn new(value: T, manager: &mut MemoryManager) -> Self {
        let size = mem::size_of::<T>();
        let align = mem::align_of::<T>();
        let ptr = manager.allocate(size, align) as *mut T;
        
        if !ptr.is_null() {
            ptr::write(ptr, value);
        }
        
        Self {
            ptr,
            manager: manager as *mut MemoryManager,
        }
    }
    
    fn get(&self) -> Option<&T> {
        if self.ptr.is_null() { None } else { unsafe { Some(&*self.ptr) } }
    }
    
    fn get_mut(&mut self) -> Option<&mut T> {
        if self.ptr.is_null() { None } else { unsafe { Some(&mut *self.ptr) } }
    }
}

impl<T> Drop for SmartPtr<T> {
    fn drop(&mut self) {
        if !self.ptr.is_null() {
            unsafe {
                ptr::drop_in_place(self.ptr);
                (*self.manager).deallocate(self.ptr as *mut u8);
            }
        }
    }
}

fn main() {
    let mut manager = MemoryManager::new();

    // Allocate memory and use smart pointers
    unsafe {
        let mut data1 = SmartPtr::new(100i32, &mut manager);
        let mut data2 = SmartPtr::new([0u8; 1024], &mut manager);
        
        if let Some(val) = data1.get_mut() {
            *val = 200;
        }
        
        println!("Value of data1: {:?}", data1.get());
        println!("Stats: {} bytes, {} allocations", manager.get_stats().0, manager.get_stats().1);
    } // data1 and data2 are dropped here, deallocating memory
    
    println!("Stats after drop: {} bytes, {} allocations", manager.get_stats().0, manager.get_stats().1);
}
```
</UniversalEditor>

### Systems Programming Differences

1.  **Memory Management**: Rust allows manual memory management with `unsafe`, while JavaScript has automatic garbage collection.
2.  **Pointers**: Rust has real pointers, while JavaScript does not.
3.  **Performance**: Rust offers fine-grained control over performance, while JavaScript's performance is managed by its engine.
4.  **Safety**: Rust's `unsafe` block allows bypassing safety checks, requiring careful handling.

---

## 🔧 The Macro System

### Procedural vs. Declarative Macros

<UniversalEditor title="Rust Macro System" compare={true}>
```rust !! rs
// Declarative macro (macro_rules!)
macro_rules! my_vec {
    ( $( $x:expr ),* ) => {
        {
            let mut temp_vec = Vec::new();
            $(
                temp_vec.push($x);
            )*
            temp_vec
        }
    };
}

// Procedural macro (custom derive)
// This requires a separate crate with `proc-macro = true`
// in Cargo.toml.
/*
extern crate proc_macro;
use proc_macro::TokenStream;
use quote::quote;
use syn;

#[proc_macro_derive(MyTrait)]
pub fn my_trait_derive(input: TokenStream) -> TokenStream {
    let ast = syn::parse(input).unwrap();
    impl_my_trait(&ast)
}

fn impl_my_trait(ast: &syn::DeriveInput) -> TokenStream {
    let name = &ast.ident;
    let gen = quote! {
        impl MyTrait for #name {
            fn hello_macro() {
                println!("Hello, Macro! My name is {}!", stringify!(#name));
            }
        }
    };
    gen.into()
}
*/

trait MyTrait {
    fn hello_macro();
}

// Using the declarative macro
fn use_declarative_macro() {
    let v = my_vec![1, 2, 3];
    println!("{:?}", v);
}

// Using the procedural macro (conceptual)
// #[derive(MyTrait)]
// struct MyStruct;

fn main() {
    use_declarative_macro();
    // MyStruct::hello_macro();
}
```
</UniversalEditor>

### Key Concepts of Macros

1.  **Code Generation**: Macros write code at compile time, reducing boilerplate.
2.  **Declarative Macros**: Use `macro_rules!` for simple pattern-based macros.
3.  **Procedural Macros**: More powerful macros for custom derives, attributes, and function-like macros.
4.  **Domain-Specific Languages (DSLs)**: Macros can be used to create embedded DSLs.

---

## ⚡ Performance Optimization

### Benchmarking and Profiling

<UniversalEditor title="Performance Optimization in Rust" compare={true}>
```rust !! rs
// Using Criterion for benchmarking
// This requires `criterion` in [dev-dependencies]
/*
use criterion::{black_box, criterion_group, criterion_main, Criterion};

fn fibonacci(n: u64) -> u64 {
    match n {
        0 => 1,
        1 => 1,
        n => fibonacci(n - 1) + fibonacci(n - 2),
    }
}

fn criterion_benchmark(c: &mut Criterion) {
    c.bench_function("fib 20", |b| b.iter(|| fibonacci(black_box(20))));
}

criterion_group!(benches, criterion_benchmark);
criterion_main!(benches);
*/

// Using `perf` for profiling (Linux)
// 1. cargo build --release
// 2. perf record ./target/release/my_app
// 3. perf report

// Zero-cost abstractions example
fn use_iterator() {
    let numbers = vec![1, 2, 3, 4, 5];
    // This iterator chain compiles down to efficient machine code
    let sum: i32 = numbers.iter().map(|&x| x * 2).filter(|&x| x > 5).sum();
    println!("Sum: {}", sum);
}

fn main() {
    use_iterator();
}
```
</UniversalEditor>

### Optimization Techniques

1.  **Benchmarking**: Use tools like Criterion to measure performance.
2.  **Profiling**: Use tools like `perf` to identify performance bottlenecks.
3.  **Release Mode**: Always compile with `--release` for production builds.
4.  **Zero-Cost Abstractions**: Use high-level features like iterators, which are compiled to efficient code.
5.  **Data Structures**: Choose the right data structures for the job. 